Heat grill. In small bowl, combine all topping ingredients; mix well. Cover; refrigerate topping until serving time.
Sprinkle both sides of each steak with seasoned salt and garlic-pepper blend. Brush both sides of onion slices with oil.
When ready to grill, place steaks and onion slices on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 8 to 12 minutes or until steaks are of desired doneness and onion slices are charred and tender, turning steaks and onion slices once or twice.
To serve, top each steak with onion slices and spoonful of topping.